Method of making a heat exchanger



Feb. 18, 1941. R. A. SANDBERG METHOD OF MAKING A HEAT EXGHANGER I Filed Oct. 21, 193'? Par 19. J'mvosuse a.

tubes to the fins.

Patented Feb. 18, 1941 UNITED STATES PATENT orricr.

METHOD OF MAKING A HEAT EXCBANGEB Bay A. Sandberg, Waukegan, 111., assignor, by

memo assignments, to Houdaille-Hershey Corporation, Detroit, Miclt, a corporation of Michigan Application October 21, 1937, Serial No. 170,181

1 Claim.

This invention relates to a method of making a heat exchanger, and more particularly to amethlike, placed within the tubes for effecting the brazing of the seams of the tubes and of the Other brazing material may also be used to insure simultaneous brazing of the fins to the tubes and of the elements of the headers to each other and to the tube ends.

It is therefore an object of this invention to provide a method for the manufacture of heat exchangers, condensers and the like, wherein the various parts and elements are first assembled with brazing material placed within the open seamed tubes and elsewhere as necessary, and the whole assembly brazed in a single operation.

Other and further important objects of this invention will become apparent from the disclosure in the following specificationand the accompanying drawing.

The .accompanying drawing illustrates a heat exchanger manufactured in accordance with the method of the present invention and the views thereof are as follows:

Figure 1 is a top plan, composite view, illustrating, at the left hand side, the finished condenser and, at the right hand side, the condenser in process of assembly, with parts broken away and in section.

Figure 2 is a fragmentary isometric view of a metal sheet from which a tube is rolled, showing tubes II, on which are mounted transversely extending sheet metal fins l2. Headers l3 and I4 receive the respective ends of the tubes H and connect pairs of said tubes to provide for a circuitous flow of the cooling or heating fluid through the heat exchanger.

In accordance with the method of this invention, each of the tubes II is formed from a strip I5 (Fig. 2) of sheets metal, such as steel, by rolling the strip into the form of an elongated cylinder, or tube, having an open seam l6 extending longitudinally thereof. The fins [2 are also formed, preferably, of relatively thin sheet metal,

such as iron or steel, and are provided with apertures I'I adapted to snugly receive the tubes ll. Struck out flanges l8 surround the apertures It .and embrace the tubes ll. Preferably, in the formation of the flanges l8, notches I9 are provided all on one side, or on opposite sides of the apertures H. The formation of the apertures l1 and notched flanges It can suitably be performed in a stampin operation.

The headers I3 and II are similarly formed, so that a description of the header M will be sufficient. Said header It comprises an inner sheet metal plate 20 having flanged apertures 2| for receiving the ends of the tubes H, The flanges 2| may project either outwardly, as shown, or inwardly, and are of such diameter as to snugly receive the ends of said tubes II. An outer plate 22 completes the header. Said outer plate 22 is provided with outwardly convex embossed portions 23 of such dimension as to embrace two adjacent flanged openings 2| of the inner plate 20, thereby connecting the corresponding tubes II. In the assembling of the header plates 20 and 22, a thin brazing shim 24 i inserted between said plates 20 and 22 to lie between and abut the plane corresponding surfaces of said plates. Said brazing shim 24 is provided with apertures 25 of substantially the same size and configuration as the openings into the embossed portions 23.

When assembling the parts of the heat exchanger, or condenser, the fins l2 are first inserted in a form, holder or jig, as shown and described in my Patent No. 2,064,036, with the flanges l8 extending in the same direction and with the notches l9 all in alignment. The tubes H are then inserted through the flanged apertures ll of said fins II, with the longitudinal seams l6 extending along the bottoms of said tubes. Brazing wires 26 are laid within said tubes H along the seams it. Other brazing wires 21 are preferably inserted through the notches l9 to iii lie along the top surfaces of the tubes ll. Said brazing wires l6 and 21, like the brazing shim 24, may be of brass, or other copper containing metal or alloy. Single turns of brazing wires 28 may likewise be inserted over the ends of the tubes ll prior to assembling the inner header plate 20 upon said ends.

After the parts have been assembled, as indi- Due to capillary action, the molten brazing metal formed by melting down the wires 26, 21 and 28, and the shims 24, flows into all of the joints formed betweenthe several parts of the unit and eflects a complete bonding at said joints. The wires IS on the insides of the tubes II, for instance, melt down and the metal thereof flows into the seams l8 and even through said seams and around the outside of the tubes II to effect the bonding of the fins I2 to said tubes H. The brazing metal of the wires 26 thus effects the closing of the open seams I6 and the excess metal assists in the brazing of the tubes II on the outside to the flanges 18. The metal of the brazing wires 21 insures a complete bonding of the flanges l8 to the outsides of the tubes II. The inner and outer plates 20 and 22, respectively, of the headers are bonded together by means of the metal provided by the shims 24, and said headers are bonded to the ends of the tubes I! by means of the brazing material supplied by the wires 28.

In Fig. 5, which shows a slight modification of my invention, a wire 30 is laid inside eachof the tubes 3| along the seam 32. Each tube, however, is provided on its outer surface with a plating layer 33 of copper, brass or other coppercontaining brazing material, which serves in lieu of an external brazing wire to complete the brazing of the tube to the fin 34. The fin 34 is apertured as at 35 to snugly receive the tube 3|, but no notches, similar to the notches l9 need be provided. The heat exchanger, after assembly of the various parts, is brazed in a single operation such as above described.

In this manner, excellent thermal joints are formed between the various connecting surfaces of the tubes, fins, and header walls and the vari ous elements of the heat exchanger are firmly.

and rigidly united into an integral whole. The use of steel for the tubes and fins, although having a lower rate of heat transfer than copper, is nevertheless justified by the lower cost of steel and the ease with which good thermal joints can be produced by the method described.

It will thus be apparent that the entire brazing operation is carried out automatically and in a single step, thereby eliminating the necessity for manually performing separate brazing operations. The brazing of the condenser in the manner described causes a simultaneous closing of the seams of the tubes II and a brazing of the fins l2 to said tubes II, as well as a brazing oi the header plates to each other and to the ends of the tubes.

Since the header plates and fins are formed by a simple stamping operation, they can be made in large quantities at very little expense by practically automatic machinery. It is also a relatively simple and inexpensive operation to form the tubes II from sheet metal, as compared with the manufacture of seamless tubing. In assembling the fins over the tubes, the edges of the seams of said tubes are brought into closely abutting relation, such that the brazing 0peration eifects a fluid tight joint.

I am aware that many changes may be made and numerous details of construction may be varied through a wide range without departing from the principles of this invention, and I, therefore, do not purpose limiting the patent granted hereon otherwise than necessitated by the prior art.

I claim as my invention:

The method of constructing a heat exchanger which comprises assembling apertured fins across open seamed tubes having an external layer of brazing material, providing brazing material within said tubes. inserting each set of adjacent ends of said tubes into a sheet metal plate having flanged apertures adapted to snugly receive said ends, superposing on each of said sheet metal plates a brazing shim having apertures adapted to register with the apertures of said sheet metal plates, superposing on each of said brazing shims an outer sheet metal plate provided with a plurality of outwardly convex embossed portions each adapted to embrace two of the flanged apertures of said sheet metal plates, and heating the assembly to cause the brazing material disposed within said tubes to flow out at the seams therein, and, together with said external layers of brazing material and said brazing shims, to braze said tubes, fins and sheet metal plates together.

RAY A. SANDBERG. 

